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Despite the increasing number of Organic Rankine Cycle (ORC) installations at megawatt scale, the waste heat rejected by industrial processes can vary substantially from a few kW to many megawatts. Hence, ORC units with a power output in the range of tens of kilowatts should be developed to tackle the opportunity for heat recovery and business opportunities that can arise from it. In the current research activity, a dynamic model of a small scale ORC system was developed using a commercial software platform. The unit is equipped with two plate heat exchangers, a centrifugal pump and a radial turbine designed and optimized using an in-house code and a commercial 1D modelling tool. The off design behavior of the ORC system has been characterized by varying the inlet conditions of heat source and sink, and the turbomachine’s revolution speeds. Moreover, the response to transient thermal inputs at different time scales has also been investigated. Finally, four control strategies have been compared from the performance and energy efficiency perspectives. The results show that the turbine based regulation strategies achieve better control performance while pump based controls are able to regulate the system by maintaining the net power output closer to the design point.

Le turbine a gas lavorano in condizioni operative estreme di temperatura e pressione per ottenere le massime prestazioni dell’impianto energetico. Tali requisiti possono risultare al limite delle condizioni di progettazione delle pale, dei cuscinetti e dei numerosi componenti presenti nella camera di combustione. Di conseguenza la loro vita in esercizio può risultare limitata, come verosimilmente risulta dalla frequenza delle fratture che tali componenti presentano rispetto alla minore incidenza verificabile in altre parti dell’impianto. I difetti, che insorgono in corrispondenza dello stadio delle pale della turbina esposto alla maggiore temperatura e pressione di lavoro, risultano attribuibili ai fenomeni di creep, di ossidazione e di danneggiamento per fatica. Inoltre non è ancora del tutto chiaro se queste azioni di danneggiamento agiscono in modo simultaneo o se alcune di esse risultano predominanti (come, quando e perché) rispetto ad altre che divengono meno influenti nel corso del danneggiamento per fatica termomeccanica (TMF). I materiali svolgono il ruolo fondamentale per l’incremento della vita in esercizio degli impianti. A tale proposito la via dell’innovazione è stata intrapresa con lo sviluppo di superleghe a base nickel ottenute per solidificazione direzionale (DS) o monocristalline (SX) e con l’impiego di rivestimenti ceramici che fanno da scudo termico al materiale sottoposto alle temperature preservando le superfici esposte dei componenti dall’ossidazione a caldo. Essi consentono di aumentare la temperatura di funzionamento degli impianti e, conseguentemente, di aumentarne il rendimento. Il vantaggio ottenuto dallo sviluppo dei nuovi materiali e dei rivestimenti va attentamente valutato mediante la messa a punto di nuove tecniche diagnostiche simulanti le condizioni di lavoro dei componenti e, in tale ambito, la fatica termomeccanica (TMF) ha dimostrato di essere un ottimo strumento diagnostico complementare di quello della fatica LCF, sinora più diffuso. Nella memoria sono descritte le procedure per l’esecuzione di prove TMF ed alcuni esempi di confronto tra TMF ed LCF per alcuni materiali innovativi impiegati in componenti turbogas.

Radial glial cells and astrocytes function to support the construction and maintenance, respectively, of the cerebral cortex. However, the mechanisms that determine how radial glial cells are established, maintained, and transformed into astrocytes in the cerebral cortex are not well understood. Here, we show that neuregulin-1 (NRG-1) exerts a critical role in the establishment of radial glial cells. Radial glial cell generation is significantly impaired in NRG mutants, and this defect can be rescued by exogenous NRG-1. Down-regulation of expression and activity of erbB2, a member of the NRG-1 receptor complex, leads to the transformation of radial glial cells into astrocytes. Reintroduction of erbB2 transforms astrocytes into radial glia. The activated form of the Notch1 receptor, which promotes the radial glial phenotype, activates the erbB2 promoter in radial glial cells. These results suggest that developmental changes in NRG-1–erbB2 interactions modulate the establishment of radial glia and contribute to their appropriate transformation into astrocytes.

Human papillomavirus (HPV) infection is one of the most common sexually transmitted infections (STIs) in young women. They can occur in one or multiple areas of the female genitalia. Usually, the vulva is the initial site of implantation for HPV. The purpose of our study is to evaluate the epidemiological aspects, incidence of single or multiple lesions in the lower genital tract, correlation between sexual behaviour and their localization and behaviour risk factors for persistence and recurrence of HPV lesions and cervical intraepithelial lesion (CIN) in a long-term follow-up among young women. We recruited 268 patients aged 11-21 years who previously had cytology and/or physical examination suspicious for HPV infection. The women were interviewed and asked information about lifestyle, sexual behaviour, work, personal or family history of genital warts and school attendance. We considered individuals to be 'smokers' if they smoked more than five cigarettes/day. No specific data were recorded about oral contraception, nevertheless, no woman had used oral contraceptives (OCs) for more than 2 years. Young women included in the study were between the age of 12 and 21 years who had HVP lesions after entry examinations and had undergone no treatment for HPV lesions prior to entry. Other exclusion criteria relevant to this study included cervical excisional treatment prior to entry or later. Two hundred and thirty-four young women were included in our study group. Our diagnostic schedule for a complete evaluation included exo- and endocervical cytology, colposcopy, directed biopsy and microcolpohysteroscopy. The treatment was performed with a LASER CO2 Coherent 400, model 451, with Zeiss photocolposcopy attachment. The finding that, among 126/234 (53.8%) adolescents using contraceptives, only 85 (36.3%) have used condom, the only barrier form of contraceptive effectively protecting against virus, shows a low awareness of the high risk for contracting HPV infection among young sexually active women. The sites most frequently affected in our study were vulva, perianus and perineum (194/234), 82.9% and the cervix (125/234), 53.4%. Vaginal lesions were detected only in 29/234 patients (12.3%). According to our data, in 161 patients, sexual habits, age at the first intercourse (P=0.68), frequency of intercourses (P=0.49) and number of lifetime partners (P=0.27) as well as age (P=0.26) play a role in transmission and incidence of HPV infection but not on the location of the lesions. This can be due to a coexistent clinical and subclinical multiple infection as well as a transmission via intercourse or from other sources, including tampons. Abnormal Pap test was related to HPV infection, but the low correlation with colposcopic and histological findings in this study justify the support of other examinations such as colposcopy and punch biopsy for diagnosis. Moreover, according to our data, cytology alone shows to be not suitable to exclude CIN (seven underestimated cases of CIN) and a closer correspondence were found between colposcopy and the result of histological sample after punch biopsy in CIN detection. More attention must be paid to psychological aspect of diagnoses and treatment among adolescents, more than older women as the high rate of patients lost shows in our study: 75/234 (32.05%) before LASER surgery and 55/159 (34.59%) during follow-up. International data shows that only 12-45% of sexually active adolescent girls have obtained Pap smear screening. In our study, we found no correlation between treatment failure and cigarette smoking or between the use of oral contraceptives and persistence/recurrence after LASER CO2 surgery. Because the small sample of our study group, further analyses were required.

The fatigue crack growth rate (FCGR) of a polycrystalline IN 718 superalloy was investigated at 650°C for two different grain sizes using single notch tension (SENT) specimens. In air the FCGR is insensitive to the grain size in the mixed time-cycle dependent regime and the oxidation-induced intergranular fracture controls the crack growth rate. When a hold time is applied the coarse microstructure shows a lower resistance to crack propagation both in air and in vacuum. A two parameter Paris equation was found to describe the relationship between the loading frequency and the crack growth rate, which provides valuable insight into the oxygen-induced intergranular fracture mechanisms operating at elevated temperature.